Refrigerating apparatus



June 1, 1943.

' Filed oct. 24, 1939 3 Sheets-Sheet l Tee f (L l I 66 62 ,5, i F H I I. 78 I g 0 0 0w -36" x CZMZMF I8 4 g l em F n E r 4%. #5

INVENTOR.

ATTORNEYS June 1, 1943. c. F. HENNEY 2,320,432

" REFRIGERATING APPARATUS Filed 001;. 24, 1939 3 Sheets-Sheet 2 uunnuuuuu [100000000 INVENTOR.

ATTORNEYS June 1-, 1943.

Filed Oct. 24, 1939 s Shets-Sheet 3 n-0000', nuuolu I" Patented June 1, 1943 REFRIGERATING APPARATUS Charles F. Henney, Dayton, Ohio, assignor to General Motors Corporation, Dayton, Ohio, a

corporation of Delaware Application October 24, 1939, Serial No. 301,016

' 5 Claims.

This invention relates to refrigerating apparatus andmore particularly to air conditioning means and controls for reducing the capacity of the system during light loads.

Air conditioning means employing mechanical refrigeration are designed for properly cooling the enclosure under extreme outside temperatures, for example, 110 F. This amount of cooling is too great for normal temperature conditions and it is therefore customary to cycle the refrigerating system in order to reduce the amount of cooling. Since the cooling unit operates above freezing temperatures and is provided with a fan for circulating the air through the passages in the cooling unit, water condenses and collects upon the cooling unit during the operation of the refrigerating system. However, when the refrigerating system is stopped, the fan continues to operate and blows and evaporates water ofl the cooling unit, thereby adding to the humidity of the air in the enclosure. This effect is increased and becomes more undesirable as the outside temperature is reduced, since it causes more frequent cycling and higher humiditles. It is therefore an object of my invention to reduce the capacity of the refrigerating system without cycling of the entire refrigerating system to reduce the refrigerant'capacity for light loads.

It is another object of my invention "to provide suitable automatic controls for controlling the reduction in capacity of a refrigerating system for air conditioning.

It is a more specific object of my invention to I11:

provide automatic controls for controlling the reduction of air circulation and :heat transfer between the cooling unit and the air in air conditioning.

It is still another object of my invention to provide suitable automatic controls for reducing the speed of refrigerating apparatus for air conditioning.

It is another object of my invention to provide automatic controls for reducing the volumetric emciency of the compressor of the refrigerating apparatus.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of the present invention is clearly shown.

In the drawings:

Fig. 1 is a diagrammatic view illustrating one form of my invention;

Fig. 2 is another diagrammatic view illustrating another form of my invention; N

Fig. 3 is a fragmentary view showing a modification of the air circulating and cooling unit of Fig. 4; and

Fig. 4 is another diagrammatic view showing another modified form of my invention.

Briefly, in Fig. 1, I have shown a mechanical refrigerating system having a finned tube evaporator through which air is circulated from the enclosure by an electric fan which has its speed controlled in accordance with inside and outside temperatures substantially in the proportions of I to 3. A variable speed drive is provided between the compressor driving motor and the compressor which reduces the speed of the compressor when the outside temperature falls. An expansion chamber controlled by inside and outside temperatures is provided on the compressor for providing a further reduction in compressor capacity. These two means may operate in steps to so that the speed is first reduced and thereafter, to provide a greater reduction in capacity, the capacity chamber is opened. However, any one or any combination of means of any modification disclosed herein may be employed to obtain desired reduction in capacity. Fig. 2 is provided with a similar cooling unit and electrically controlled fan. In this system,

the speed of the compressor driving motor iscontrolled by a variable resistance in accordance with changes in inside and outside temperature to provide further reduction in capacity. Restricted by-passes controlled by thermostatically controlled valves arranged to operate in steps are also provided.

In Fig. 4, the fan circulates the air through two cooling units which are connected to independent refrigerating systems. These systems are controlled so that they are stopped in steps so that first one, system stops and at a lower temperature the second system stops so that the reduction in capacity is in several steps rather- 'and at the other end is connected to a centrifugal fan 26 which is driven by an electric motor II. The fan 26 draws air from the enclosure and forces the air through the finned passages in the cooling unit 22, after which the air is discharged through the duct 24 into the enclosure.

The cooling unit 22 is supplied with liquid re frlgerant by a liquefying means which includes the compressor 30 driven through pulley and belt means by the electric motor 32. The refrigerant is withdrawn from the cooling unit 22 through the suction conduit 34 by the compressor and pumped into the condenser 36 where the compressed refrigerant is liquefld and collected in the receiver 38. From the receiver '38 the liquid refrigerant is supplied through a liquid supply line 40 under the control of an automatic ther mostatic expansion valve 42 to the cooling unit 22.

The electric motor 32 is supplied with electric energy through the common conductors 44 and 44 and the branch conductors 48 and 50 which connect to the common conductors 44 and 46. The electric motor 28 which drives the fan 26 is supplied with electric energy through the common conductors 44 and 46 and through the branch conductors 52 and 54. A switch is provided for deenergizing both motors.

Heretofore, it has been customary to control therefrigerating system by a switch 56 placed in series with one of the branch conductors and controlled by a thermostat bulb 58 in the enclosure 20. It was found, however, that such a system cycled frequently under ordinary condi tions producing an undesirable fluctuation in temperature and humidity, and particularly provided undesirably humid conditions within the enclosure. One of the particularly objectionable features of this arrangement was that moisture would condense upon the cooling unit 22 and accumulate during the operating cycle of the system and when the compressor was stopped the fan 26, which would remain in operation, would blow and evaporate the accumulated water and condensation oil. the cooling unit into the air in the enclosure. This provided an undesirable increase in the humidity in the enclosure and in general provided an average humidity which was higher than comfortable under light load condi tions when the outside temperature was much less than the maximum temperature conditions for which the system was designed. For example, it is customary to design a system to provide adequate cooling capacity for an outside temperature of 110 F. whereas normally the temperature isonly 80 F. or 90 F. during most of the summer. v tions, this frequent cycling took place with the undesirable humidity conditions being produced by such a system.

As a first step in preventing the frequent cycling of the compressor and for reducing the humidity under low temperature conditions, I have provided a means for reducing the speed of the motor 28 and the fan 26 which circulate the air through the flnned passages of the cooling unit 22. This reduces the amount of air flowing through the cooling unit and therefore causes a greater reduction in temperature of this air and more moisture condensation so that more mois-. ture is removed from the'air by the cooling unit and the humidity condition is thereby avoided. While any of the diflerent forms of speed reduction of an electric motor may be employed, I have shown for purposes of illustration an automatic rheostat including a resistance coil 60 and a tap Therefore, under normal condiinlet of the lows 88.

'2 which is in the form of a lever operated by the ing to a thermostat bulb 66 located inside the enclosure 20 and a thermostat bulb 68 located outside the enclosure 20.

Preferably, these bulbs are each charged with activated charcoal and the system is charged with some suitable non-condensible gas, such as carbon dioxide. Preferably, the amount and effectiveness of the charcoal in the bulb 68 is approximately three times the amount and eifectiveness of the charcoal in the bulb 66, since it is desirable that the efiective control of the fan 25 be in that proportion to inside and outside temperatures. These bulbs may be ordinary dry bulbs or they may be responsive to effective temperatures or to wet bulb temperature if desired. If the compressor capacity is unchanged, the rheostat 60 may be proportioned to provide a reduction in air circulation through the cooling unit 22 of about 25% or more. However, if means are provided for decreasing the capacity of the compressor as illustrated in Fig. 1, the speed and capacity of the fan may be reduced to provide a reduction in air circulation of as much as 50% or more. As an alternative, the speed and capacity of the fan 26 may be controlled by a humidity device in response to relative or absolute humidity within the enclosure.

In order to provide a reduction in capacity of the coinpressor 30, I have provided a variable speed drive between the driving motor 32 and the compressor 30. In order to do this, I have employed a V-belt and V-belt type pulleys. The pulley 10' upon the motor 32 has one or both flanges axially movable with the flanges held in engagement with the sides of the belt by a coil filled with activated charcoal and the system is charged with carbon dioxide. Preferably, the bulb is provided with charcoal having three times the adsorption capacity of the charcoal in the bulb 82 so that changes in the outdoor temperature will have three times as much effect as changes in the inside temperature. Instead of controlling by temperature, a humidity device responsive to relative or absolute humidity within the enclosure may be used to control the speed reduction.

In order to provide an additional reduction in compressor capacity beyond the limits of a speed reducing device, I provide a capacity chamber 84 which is connected to the compression space of the compressor cylinder by a port which is normally closed by a valve 86 operated by the bel- This bellows is connected to the bulbs and 92. The bulb 90 is located outside the enclosure 20 and contains activated charcoal having an adsorption capacity preferably about three times the activated charcoal contained in the bulb 92 which is located inside the enclosure 20. The bellows 88 and the bulbs 90 and 92 are preferably charged with a gas, such as carbon dioxide, which can be adsorbed and evolved from the charcoal according to changes of temperature. All of these bulbs may be either wet or dry or made responsive to effective. temperature or relative or absolute humidity.

When the speed reduction device for the electric motor 28 is used in connection with the speed' reducing means forming a part of the belt drive between the motor 32 and the compressor 30, a

speed reduction of as much as 50% may be provided for both the fan motor 28 and the compress01 30. This will greatly reduce the cycling of the compressor 30 under the control of the thermostat 58; It will also prevent the high humidi which draws air from the enclosure I and forces it through the evaporator I22 after which the cooled air is discharged from the duct I24 in the enclosure I20. As before, the fan is driven by an electric motor I26 which is under the control of a rheostat I60 provided with a tap lever i62 for varying the resistance .of the rheostat under the control of the bellows I64 which is connected to the bulbs I66 and I68. The bulb I66 is preferably located outside the enclosure I20 so that it is responsive to outside air temperature while the bulb I66 is mounted within the enclosure I20. As mentioned before, the bulb I63 may contain activated charcoal having an adsorption capacity about three times that, of: the

charcoal provided in the bulb I66. This bulb system is preferably charged with carbon dioxide or some other suitable gas for this purpose.

The evaporator I22 is supplied with liquid refrigerant by liquefying means which includes'the compressor I30 driven by arr-electric motor I32 for withdrawing evaporated refrigerant through the suction conduit I34 and for forwarding the compressed refrigerant to the condenser collected in the receiver I36. The liquidrefrigerant is forwarded to the evaporator I22 through the liquid supply conduit I under the control of the thermostatic automatic expansion valve I42. In order to reduce the capacity of the compressor under light load conditions, I provide a rheostat I69 which is similar to the rheostat I and is located in series with the compressor driving motor I32 for reducing the speed of this motor.

This rheostat includes a tap lever III operated by the bellows I13 under the control of the thermostat bulbs I15 and I11. Each of these bulbs preferably contains activated charcoal and carbon dioxide. The bulb I11 is located outside the enclosure I20 so that it is responsive to outside air temperature and is preferably provided with activated charcoal having three times the ad- I36 where the compressed refrigerant liquefles and is sorption capacity of the charcoal provided in the bulb I15 located within the enclosure I20. rheostat I69 may also be used for stopping the compressor when the speed of the motor I32 is reduced to a predetermined minimum. amount. Preferably, the speed of the motors I28 and I32 are reduced to about 50% to provide a reduction in refrigerating capacity to prevent short cycling of the compressor and to avoid high humidity conditions under light loads.

In order to provide a further reduction in refrigerating capacity, I provide two restricted bypasses I19 and |6I which connect the suction conduit I34 and the conduit I35 connecting the The steps. sure 220 containing a duct 224 through which the branch liquid lines.

outlet of the compressor and the condenser I36. The by-pass I19 is controlled by valve I63 operated in accordance with the temperatures of the thermostat bulbs I and I81 located respectively outside and inside the enclosure I20. These bulbs are charged similarly to the other bulbs in the proportion of about 1 to 3 or some other desired proportion. Likewise, the by-pass IN is provided with a valve I89 operated in accordance with the temperature of thebulbs I9I and I93 located respectively inside and outside the enclosure and charged in a manner similar to the bulbs I85 and I81. These bulbs may be dry bulbs, wet bulbs, or responsive to effective temperature,

or controls'responsive to relative or absolute humidity within the enclosure may be used. Preferably, these valves do not open until after substantially the maximum speed reduction of the motor I32 is attained and then first one valve will open to attain further reduction in capacity, after which the other valve will open to attain an additional reduction in capacity. In' this way, the capacity of the system is reduced, short cycling is prevented and the humidity can thus be kept within desired limits.

In Fig. 4 there is provided another means for providing a reduction in capacity in the form of In this figure, there is provided an enclo are mounted in series within the duct 224 so that the air drawn from the enclosure 220 will pass through both evaporators 222 and 223, after which it is discharged again in the enclosure. These two evaporating means are connected to separate refrigerating systems, but if desired, they may be connected in multiple or series relation in a single refrigerating system. When connected in multiple, the common suction line may be provided with a valve for maintaining a desired pressure in the evaporators and a shut-off thermostatic valve may be provided in one of A by-pass provided with an automatic expansion valve may then be used between the common liquid line and the compressor inlet.

As shown, the evaporator 223 is connected by a suction conduit 225 to a compressor 221 driven by an electric motor 229. The compressor 221 withdraws evaporated refrigerant from the evaporator 223 through the suction conduit 225 and the compressed refrigerant is liquefied in the condenser 23I and collected in the receiver 233. A liquid supply conduit 235 conducts the liquid refrigerant from the receiver 233 to the inlet of the evaporating means 223 under the control of the thermostatic automatic expansion valve 231.

The evaporator 222 is connected by the suction conduit 234 to the compressor 230 driven by the electric motor 232. This compressor 230 withdraws evaporated refrigerant from the evaporator 222 through the suction conduit 234 and forwards the compressed refrigerant to the condenser 2-36 where the compressed refrigerant is liquefied and collected in the receiver 238. The liquid in the receiver 238 is conducted through the liquid supply conduit 240 to the inlet of the evaporator 222 under the control of the thermostatic automatic expansion valve 242. While these systems have been described as being of the widely used dry expansion type, other types of refrigerating systems may be used if desired.

In this arrangement, I-have again provided a rheostat 260 controlled by the tap lever 262 operated by the bellows 264 under the control of the charcoal filled bulbs 266 and 268 located inside and outside the enclosure for reducing the speed of the motor 228 and the fan 226 as the temperature and the refrigerating load becomes less. This causes a reduction in air-flow through each of the evaporating means 222 and 223 and thereby reduces the load on the compressors and thus permits the. operation of the systems atlower back pressures and lower evaporator temperatures which causes more condensation of moisture from the air flowing over the evaporator surface, thus reducing the humidity to a greater extent. The operation of the systems at lower back pressures also reduces their capacity and the cycling of the compressor.

However, in order to provide a further reduction in capacity as the temperatureis lowered, the system including the evaporator 223 is stopped when the temperature and the air within the en- 1 closure reaches a certain limit. For this purpose,

a snap-acting switch 21l operated in accordance with the temperature thermostat bulb 213 within the enclosure 220 is provided. This bulb 213 and switch 21! may operate in accordance with dry, wet bulb or effective temperature or relative or absolute humidity. This switch is connected in series with the motor 229 which drives the compressor 221. Thus, by this switch 211,- when the temperature of the air within the enclosure 220 reaches a certain limit, the compressor 221 is stopped, thus stopping evaporation within the evaporator 223. The other system connected to the evaporator 222 continues its operation after the switch 21! is open. This other system, howcordance with the temperatures of the charcoal and carbon dioxide filled thermostat bulbs 212 and 214 located outside and inside the enclosure 220. Preferably, the charcoal in the bulb 212 has approximately three times the adsorption capacity of the charcoalin the bulb 214. All of the bulbs in this system maybe ither dry bulbs, wet bulbs or effective temperature bulbs so that they may be responsive to temperature or humidity or a combination of temperatureand humidity. The switch 210 is so set that it will cycle only at temperatures below the temperature at which switch 21 I. opens. Thus,-at the lower temperatures, the evaporator 222 will cycle after the evaporator 223 becomes inoperative. paratively long since only a part of the refrigerating capacity is being used. This'system is quite eflicient since short cycling is prevented and each system operates at substantially its maximum efliciency whenever it is in operation.

In Fig, 3, I have shown a modified arrangement of the two evaporators in the duct 224. In this arrangement, the evaporator 222a is placed above the evaporator 223b, In this figure, the evaporator 222a corresponds to the evaporator 222 and is connected to a similar refrigerating system while the evaporator 223b corresponds to the evaporator 223 and is connected to a similar refrigerating system. Thus, in this arrangement, when the air is circulated through the duct 224 by the fan 226, the air will flow through the evaporators 222a and 2231) in parallel. When both evaporators are in operation, the effect will be substantially the same as in Fig. 4. However, when evaporator 2231) becomes inoperative, the

These cycles will be comever, is also provided with a snap acting switch I 210 connected in series with the motor 232. This switch 210 is connected to and operated in acair will pass through its passages without being materially cooled. This air, therefore, will be relatively warm and will tend to rise. However, the air passing through the evaporator 222a'will be cooled and will tend to fall. Thus, after passing through the evaporators, the air will tend to mix because the upper air will be cooled and will tend to fall and the lower air will be 'warm and will tend to rise. This arrangement has the further advantage in that a greater amount of dehumidiflcation will be performed, since only onehalf the air passes through the evaporator 222a and, therefore, this air will be cooled to a greater extent than in the arrangement shown in Fig. 4.

While the form of embodiment of the invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

What isclaimed is as follows:

l. Refrigerating apparatus for an enclosure to be cooled and dehumidified comprising in combination, an evaporator, a condenser, a compressor, refrigerant flow connections between said evaporator compressor and condenser, fan means for flowing air over said evaporator, means responsive to the dry bulb temperature in said enclosure for varying the flow of air over said evaporator, and means responsive to the dry bulb temperature of the air for passing a portion of the refrigerant directly from the high side of said compressor to the low side of said compressor.

2. Refrigerating apparatus for an enclosure to be cooled and dehumidified comprising in combination, evaporator means,condenser means,.

compressor means, refrigerant flow connections between said evaporator means, condenser means and compressor means, means for flowing air to be conditioned in thermal exchange with said evaporator means, means influenced by the outside air temperature for reducing the rate of cooling of the air by said evaporator as the outside air temperature decreases, means forbypassing a portion of the refrigerant discharged by said compressor means directly to the intake of the compressor, and means responsive to the inside air temperature controlling the flow of refrigerant through said by-pass.

3. In combination, evaporator means, condenser means, a compressor, refrigerant flow connections between said evaporator means, condenser means and said compressor, means for flowing air to be conditioned in thermal exchange with said evaporator means so as to cool and dehumidify said air, means for varying the amount of air cooled and'dehumidified by said evaporator means, means for varying the effective output per stroke of said compressor, and means for varying the speed of said compressor, said last named means including means responsive-to the outdoor air temperature.

4., Refrigerating apparatus for an enclosure to be cooled and dehumidified comprising in combination, evaporator means, condenser means, a compressor, refrigerant flow connections between said evaporator means, compressor and condenser means, fan means for flowing air to be cooled and. dehumidified in thermal exchange with said I evaporator means so as to cool and dehumidify the air, means for decreasing the rate of cooling of said air bysaid evaporator means as the outside air temperature decreases, and means responsive to the temperature of the air in said enclosure for passing a portion of the refrigerant with said evaporator means so as to cool and 10 dehumidiiy the air, means for decreasing the rate of cooling of said air by said evaporator means as the outside air temperature decreases, means responsive to the temperature of the air in said enclosure for passing a portion ofthe refrigerant directly from the high side ofsaid compressor to the low side of said compressor, and means for varying the speed of said compressor.

CHARLES F. HENNEY. 

